Research On Preparation And Energy Storage Performance Of Transition Metal Selenides And Composites

Due to the development of science and technology,the traditional fossil energy is gradually exhausted.There is an urgent to need develop renewable energy sources and their energy storage devices.Supercapacitor is a promising energy storage device.Nevertheless,the low energy density of supercapacitor seriously limits its large-scale commercial application.The core of supercapacitor is the electrode material,which affects the performance of energy storage.It has become the important field of research.Besides,transition metal selenides have received much attention due to their excellent theoretical specific capacitance.In this paper,the transition metal selenides and their composite nanomaterials are prepared.To improve their performance for energy storage,their compositional structure and preparation process are investigated.The main studies are as follows:(1)The NiCoSe₂ on carbon cloth was in-situ grown by a simple and effective electrodeposition method.Due to the excellent synergy between Ni and Co elements were utilized to construct highly efficient energy storage electrode materials.The electrode exhibited an area specific capacitance of 1250 m F cm^-2 by a three-electrode test.Moreover,its capacitance retention was 85.1%after 2500 charge/discharge cycles.Asymmetric supercapacitor was assembled with activated carbon(AC)and Ni Co Se₂,at the same time,the supercapacitor achieved an area specific capacitance of 387.1 m F cm^-2 and a retention rate of 96.1%after 3000 charge/discharge tests.(2)To prepare the NiCoSe₂@NiCo-LDH@CC with core-shell structure by electrodeposition and hydrothermal method.The higher intrinsic conductivity Ni Co Se₂serves as a support skeleton,which improves the electron transfer capability,and Ni Co-LDH provides a larger specific surface area with more ion transport paths.By assembling with AC electrode,the supercapacitor exhibited an area specific capacitance of 912.5 m F cm^-2.After 2000 cycles,the cycled capacity can still maintain 96.1%of the original capacity.It had an excellent cycling performance and greatly improved the stable cycling performance of Ni Co-LDH,which showed a good application prospect.(3)A NiZn-LDH/NiCoSe₂ composite was synthesized on nickel foam by hydrothermal and electrodeposition method.In order to enhance the overall electrochemical performance,the higher electrical conductivity Ni Co Se₂was selected as composite layers.The capacitance of 2980 F g^-1 and capacity retention of 83.1%after 4000 cycles were obtained in a three-electrode configuration.By assembling with AC electrode,the Ni Zn-LDH@Ni Co Se₂//AC supercapacitor exhibited a specific capacitance of 136.3 F g^-1.After 8000 cycles capacity test,its capacity was about 91%of the original capacitance,which showed potential application in the field of supercapacitors.